EP3682991A1 - Ring and socket for tightening by radial expansion - Google Patents

Abstract

The present invention relates to a clamping ring (1) and retaining intended to take place in a cylindrical housing (3) made in the base (5a) of a part (5) that it is desired to immobilize relative to a body , this ring (1) being formed from a series of successive adjacent cylindrical and / or pseudo-cylindrical elements (7, 9) which are linked together and whose base surface is omega-shaped and thus has a top (7a, 9a) and two branches (7b, 7c), the tops of these elements (7, 9) being alternately arranged on the outside and on the inside of the ring and respectively forming an external element (7) and a internal element (9). This clamping ring is characterized in that the branches (7b, 7c) connecting two adjacent elements are common and the external elements (7) and the internal elements (9) form “shells” the thickness of which is between 10% and 25% of the width (a) of the vertices (7a) of the external elements (7).

Description

The present invention relates to a ring and a sleeve implementing the latter which are intended to ensure the clamping with a view to holding a part, in particular a part to be machined, on a carrier device, such as in particular a mandrel, and in applying the base of this part against a bearing plane of this device, and this from a cylindrical housing hollowed out in the base face of said part, in which said ring takes place.

Devices have been proposed ensuring the maintenance of a part relative to a reference plane, or carrier plane, which comprises for this purpose a cylindrical gripping element which is received in a housing of the same shape and dimensions hollowed out in the face. base of the room.

Such gripping elements comprise, on their periphery, a part consisting of an elastomer which deforms radially under the action of an actuator, in particular axially movable, so that its cylindrical part comes to be applied with force. against the cylindrical part of the workpiece housing, thus ensuring the locking of the latter.

These gripping elements, in addition to the fact that they exert no axial force on the part to be maintained allowing the base of the latter to be applied on a reference plane, are not able to ensure a maintenance achieving a precise and repetitive positioning.

Clamping devices have also been proposed ensuring both a maintenance of the part and an application of the base thereof against a plane of reference. These clamping devices also have a cylindrical gripping element whose outer surface is formed of a multiplicity of independent segments, or jaws, which are able to move radially on the one hand and axially on the other hand under the action of 'an axially movable control member.

If such devices ensure both a radial maintenance of the part and an application of the base of the latter on a reference plane, and are therefore usable for maintaining and positioning the part which is repetitive , however, they are not sufficiently precise since the manufacturing tolerances of the part must be ultra precise, of the order for example of a few μm, insofar as the deployment of the various clamping segments has revealed to be particularly sensitive to the various disturbances to which these devices are usually exposed in machining centers, such as in particular filings, dust etc ...

We also know from patents CH 587094 , US 2612376 and CH 454570 clamping rings which are formed of a succession of clamping elements linked together. However, these clamping elements, due to their massive constitution, are not able to undergo significant radial dimensional variations under penalty of exceeding their elastic limit which implies either non-reversibility of the ring or outright rupture thereof. .

The present invention aims to provide a ring and a clamping sleeve capable of undergoing dimensional variations of the order of 1 to 2% of their diameter and allowing to achieve the clamping of a workpiece which ensures the both precise and repetitive maintenance of it as well as the application of its base on a reference plane.

The present invention thus relates to a clamping and retaining ring intended to take place in a cylindrical housing made in the base of a part that it is desired to immobilize relative to a body, this ring being formed from a series successive adjacent cylindrical and / or pseudo-cylindrical elements which are linked to each other and whose base surface is in the shape of an omega and thus comprises a top and two branches, the tops of these elements being alternately arranged on the outside and on the inside of the ring and respectively forming an external element and an internal element, characterized in that the branches connecting two adjacent elements are common and the external elements and the internal elements form “shells” the thickness of which is between 10% and 25% of the width of the tops of the external elements.

According to the invention at least the external elements or the internal elements will be of cylindrical shape. Furthermore, the external elements or the internal elements may be of pseudo-cylindrical shape.

In one embodiment, the branches which connect two adjacent elements could be "S" shaped. In another mode of implementation, these branches could be rectilinear.

Finally, the inner face of the walls of the internal or external elements having a top as a base may include an extra thickness.

The present invention also relates to a clamping sleeve implementing a clamping ring as defined above, this ring being able to be extended axially on one side of the latter by a leg ending in feet. These feet may be oriented radially towards the outside or towards the inside of the socket.

The present invention also relates to a clamping device intended to hold a part and to apply it to a load-bearing plane, the base of the part being hollowed out of a cylindrical housing receiving a clamping ring such as as defined above, this device may include a cylindrical mandrel body hollowed out with an axial bore in which a piston will be slidably mounted, the frustoconical head of which may bear against a frustoconical internal surface of the clamping ring, control means being capable of moving this piston axially so as to exert on the internal surface of the clamping ring a radial force capable of deforming it radially and applying its external surface against the cylindrical wall of the housing and the base of the part against the bearing plane.

The present invention also relates to a clamping device intended for holding a part whose base is hollowed out of a cylindrical housing receiving the clamping ring of a clamping sleeve as determined previously, this device possibly comprising a body of cylindrical mandrel, one end of which will be provided with a boss around which the legs of the clamping sleeve will take place, which end in feet which will be applied against the mandrel body, the base of the part to be held coming from resting on one face of a collar, the other face of which will itself rest on the mandrel body, the latter being hollowed out with an axial bore in which a piston will be slidably mounted, the frustoconical head of which will rest against the frustoconical internal surface of the ring, control means being able to move this piston axially so as to exert on the internal surface of the ring a radial force able to deform it radially and apply its outer surface against the cylindrical wall of the housing. By elsewhere, the feet can be kept pressed against the mandrel body by the collar.

• la figure 1 est une vue de dessus d'une bague de serrage suivant l'invention,
• la figure 2 est une vue en perspective de la bague de serrage représentée sur la figure 1,
• la figure 3 est une vue partielle agrandie de la bague de serrage représentée sur les figures 1 et 2,
• la figure 4 est une vue de face d'une variante de réalisation d'une bague de serrage suivant l'invention,
• la figure 5 est une vue partielle agrandie de la bague représentée sur la figure 4,
• la figure 6 est une vue en coupe axiale et longitudinale d'un mandrin de serrage d'une pièce à usiner mettant en oeuvre la bague de serrage suivant l'invention, le mandrin étant représenté dans une position de préserrage,
• les figures 7 et 8 sont des vues en perspective de deux variantes de mise en œuvre d'une douille de serrage suivant l'invention,
• la figure 9 est une vue en coupe axiale et longitudinale d'un mandrin de serrage d'une pièce à usiner au moyen d'une douille de serrage suivant l'invention, le mandrin étant représenté dans une position de préserrage,
• la figure 10 est une vue en coupe axiale et longitudinale partielle du mandrin de serrage de la figure 9, qui est représenté en position de serrage.

Embodiments of the present invention will be described below, by way of nonlimiting example, with reference to the appended drawing in which:

• the figure 1 is a top view of a clamping ring according to the invention,
• the figure 2 is a perspective view of the clamping ring shown in figure 1 ,
• the figure 3 is an enlarged partial view of the clamping ring shown in figures 1 and 2 ,
• the figure 4 is a front view of an alternative embodiment of a clamping ring according to the invention,
• the figure 5 is an enlarged partial view of the ring shown in figure 4 ,
• the figure 6 is a view in axial and longitudinal section of a chuck for clamping a workpiece implementing the clamping ring according to the invention, the chuck being shown in a pre-tightening position,
• the figures 7 and 8 are perspective views of two alternative embodiments of a clamping sleeve according to the invention,
• the figure 9 is an axial and longitudinal sectional view of a chuck for clamping a workpiece by means of a clamping sleeve according to the invention, the chuck being shown in a pre-tightening position,
• the figure 10 is a partial axial and longitudinal sectional view of the clamping mandrel of the figure 9 , which is shown in the clamping position.

The figure 1 represents an exemplary embodiment of a clamping ring 1 according to the invention. This ring is intended to take place in a cylindrical housing 3 which is hollowed out in the base 5a of a workpiece 5 that it is desired to hold, as shown in figures 6 .

The ring 1, which is shown in front view on the figure 1 and in perspective on the figure 2 , forms a ring whose outer surface, in the present embodiment, is of cylindrical shape and of an outer diameter equal to the diameter of the cylindrical housing 3 and the inner surface is of frustoconical shape as explained below .

More precisely, the clamping ring 1 is formed from a series of successive elements which are joined together. The base area of each of these elements, which is shown on the figure 3 , is Ω shaped so that it has a vertex and two branches. These different elements are arranged such that the top is alternately arranged on the outside and on the inside of the ring 1 so that the internal surface of each Ω is alternately open towards the inside and towards the outside of the ring. Ring.

There is thus an outer top 7a whose ends are connected to two branches 7b and 7c and an internal top 9a provided with the same two branches 7b and 7c, since the latter are common to two adjacent elements.

This base surface thus defines, with the generatrix represented by the height h of the ring 1, cylindrical elements, namely a cylindrical element 7 called the external element which is associated with the external apex 7a and a cylindrical element 9 called the internal element which is associated with the. internal vertex 9a of the base. The thickness of the tops 7a and 9a as well as the thickness of the branches 7b and 7c are substantially equal and of low value and are between 10% and 25% of the width a of the outer crown 7a.

Under these conditions, it is understood that the structure of the external 7 and internal 9 cylindrical elements is of the type Hereinafter referred to as "shell" that is to say of a small thickness. Such a structure is particularly advantageous in that it makes it possible to give the ring good elasticity allowing it a significant radial deformation while remaining within the range of its elastic deformation, which allows it in particular to ensure effective clamping of the parts. to be maintained as explained below.

It will be noted that the internal elements 9, due to the taper of the internal surface of the ring, are not strictly cylindrical and will be qualified in the present text as "pseudo-cylindrical", that is to say that these elements are cylindrical in shape except for the internal surface associated with their top 9a. This frustoconical surface serving, in the present embodiment of the invention, to ensure the radial deformation of the ring as explained below.

As shown on the figures 1 to 3 and in particular on the latter, the branches 7b and 7c are generally of the radial type but may have an "S" structure, the part of the branches close to the top being, seen from the outside, of convex shape and the opposite part. near the end being concave in shape.

Such an arrangement makes it possible to further improve the deformation capacity of the ring. It will be understood that in this arrangement and unlike the rings of the prior state of the art, the branches work in part in bending, which has the consequence of further improving their flexibility and therefore their capacity for radial deformation.

By playing on the importance of the S-shaped curvature, as well as on the thickness of the wall of the shell forming the external elements 7 and the internal elements 9, the user will thus have the possibility of controlling the deformability of the ring, and this depending on the type of tightening it wishes to perform.

It has been found that in such a shell-type structure the maximum stress zones undergone by the ring during its radial deformation were located at the level of the middle of the respective vertices 7a and 9a of the external cylindrical elements 7 and of the internal pseudo-cylindrical elements. 9. In order to improve the resistance of these elements, an extra thickness 11 has been produced at the center of the internal surface of the vertices 7a and 9a.

According to the invention, when the user wishes to increase the rigidity of the clamping ring, he has the possibility of reducing the curvature of the S- shaped branches and of arriving, as shown in the figures 4 and 5 to branches 7b, 7c which are rectilinear.

One represented on the figure 6 , by way of example, an embodiment of the clamping ring 1 according to the invention applied to the production of a mandrel 15 intended to ensure the maintenance of a workpiece 5. For this purpose, thus as specified above, the base 5a of the latter is hollowed out with a housing 3 intended to receive the clamping ring 1.

The mandrel 15 comprises a cylindrical mandrel body 17 which is disposed in an orifice 18 of a tool holder 20 in which it is fixed by screws 23.

The upper part of the mandrel body 17 ends in a cylindrical boss 19 around which is arranged a support ring 21 on which is arranged the clamping ring 1.

The mandrel body 17 is hollowed out with an axial bore 25 in which a cylindrical control piston 27 is slidably mounted and whose upper end, in the drawing, is provided with a head 29 of larger diameter and of external shape. frustoconical, the angle of inclination of this truncated cone with respect to the longitudinal axis yy 'of the mandrel being identical to that of the internal bore of the clamping ring 1.

A plate 31 forming a cover and comprising two circular bosses, namely an upper boss 31a and a lower boss 31b, is secured to the mandrel body 17 by a screw 33 with the interposition of a spacer 35.

The axial bore 25 of the mandrel body 17 opens at its lower part into an axial bore 37 of larger diameter which opens to the outside. A piston base 39, the periphery of which is provided with a seal 40 with the axial bore 37 is arranged in the latter and is fixed to the base of the piston 27 by a screw 41. A fluid supply channel hydraulic pressure 43 opens into the bore 37.

The latter is closed by a cover 45 which is fixed to the mandrel body by screws 46. This cover 45 comprises a boss 47 which penetrates into the bore 37 and which is provided with an O-ring 49 ensuring the sealing of this bore with the outside. Furthermore, the cover 45 is crossed by a hydraulic fluid supply channel 51.

It is understood under these conditions that, when the hydraulic fluid is admitted into the bore 37 through the supply channel 43, it moves the control piston 27 downwards, so that the frustoconical periphery of the head 29 thereof ci exerts on the clamping ring 1 a force normal to its contact surface breaking down into a radial force which deforms the clamping ring 1 and applies it against the cylindrical internal wall of the housing 3 and an axial force which applies the base of the clamping ring 1 against the support ring 21, ensuring the maintenance of the workpiece 5 in this position.

When, in particular after machining, it is desired to release the part to be machined 5, the arrival of the pressurized fluid is reversed by admitting it through the supply channel 51, which has the effect of lifting the piston 27 However, if the taper of the contacting surfaces of the clamping ring 1 and the piston head 29 is small, these two elements may adhere to each other and the clamping ring 1 then lifts up. the same time as the piston 27, and this until the upper surface of the clamping ring 1 comes into contact with the lower circular boss 31b of the cover, which has the effect of separating them.

The plate 31 thus performs two functions, namely a cover function ensuring protection of the device against dirt and polluting elements and a function of separating the clamping ring 1 and the piston head 29 during the dismantling phase. of room 5.

It would of course also be possible to use actuation means in which the taper of the clamping ring 1 and of the piston head 29 are reversed.

One represented on the figure 7 a clamping sleeve 1a which consists of a clamping ring 1, as described above, which is extended on one of its sides, namely downwards in the figure, by a retaining part 54 which is formed by jambs 55 which end in feet 57 facing outwards, the role of which will be explained below.

One represented on the figure 9 an example of application of this clamping sleeve in a mandrel of the same type as described above and the same references will be kept for this example.

In this application, the legs 55 of the retaining part 54 of the clamping sleeve 1a fit into the boss 19 of the mandrel body 17 and the feet 57 thereof bear against the upper face of the mandrel body .

A retaining collar 59 comes to rest on the mandrel body 17, with which it is fixed by screws 61. A bore 63 is made at the base of the collar 59 so that the latter can rest on the feet 57. of the retaining part 54, so as to ensure its fixing relative to the mandrel body 17.

The upper face 59a of the retaining collar 59 further forms a receiving plane intended to receive the base 5a of the workpiece 5. Thus, in this embodiment of the invention, the collar 59 performs two functions, namely a function of retaining the feet 57 of the clamping sleeve 1a and a function of receiving plane of the workpiece 5, thus ensuring precise positioning of the latter along the axis yy 'of the chuck.

It will be noted that the respective diameters of the piston head 29 and of the frustoconical internal bore of the clamping sleeve 1a are such that, in the pre-tightening position, as shown in FIG. figure 9 , there is a clearance between the base of the piston head 29 and the upper face of the boss 19, clearance allowing a subsequent vertical displacement of the piston 27, as explained below.

To apply the workpiece 5 against the upper face 59a of the retaining flange 59 and hold it there in this position, and as explained previously, the piston 27 is lowered by admitting the hydraulic fluid into the bore 37 by the supply channel 43, so that the frustoconical periphery 29a of the piston head 29 exerts on the clamping ring 1 of the sleeve 1a a force normal to its contact surface breaking down into a radial component and an axial component. These radial and axial forces are retransmitted to the workpiece 5 by bush 1a, which has the effect, as shown in figure 10 , on the one hand to apply the base thereof against the upper face 59a of the retaining flange 59, ensuring the function of receiving plane and on the other hand to ensure the maintenance of the workpiece 5 in this position.

As in the previous example, when it is desired to release the part 5, the supply of hydraulic fluid from the channel 43 to the channel 51 is switched over and the hydraulic fluid then lifts the piston 27 which thus releases the clamping ring 1. of the sleeve 1a from any radial force, so that the latter is at the same time detached from the workpiece 5.

It is of course also possible to use a clamping sleeve in which the feet 57 arranged at the end of the legs are no longer oriented towards the outside but towards the inside of the sleeve, as shown in FIG. figure 8 .

The present invention thus makes it possible, owing to the "shell" -type structure, to produce cylindrical and / or pseudo-cylindrical elements which have an excellent capacity for radial deformation, thus making it possible to form rings and clamping sleeves which can have a capacity of axial expansion, or contraction, of the order of 1% to 2% of their diameter.

It is thus possible for the designer to adjust the rigidity of the ring and of the clamping sleeve as a function of the radial clamping force that he wishes to transmit and as a function of the desired expansion thereof.

For a given material of the ring and / or the clamping sleeve and for a determined diameter of the latter, will thus be able to play on the number of elements used as well as on their shape and of course on the thickness of the shells constituting the cylindrical and / or pseudo-cylindrical elements.

Preferably, the clamping sleeve may be made of a spring steel, in particular a steel with a high silicon content, such as for example a steel of the type called 45SCD7 or any other steel with a high elastic limit.

Of course, the device for actuating the clamping sleeve can make use of means other than a piston with a frustoconical head acting on a complementary frustoconical part of the clamping sleeve. It is thus possible, according to the invention, to use actuating means of the cylindrical type, the increase in diameter of which would exert a radial force on the internal surface of the clamping sleeve.

It would also be possible to use actuation means using an inverted frustoconical surface.

Furthermore, the clamping ring could be made up of internal and external elements which would both be entirely cylindrical.

Finally, the ring and the clamping sleeve according to the invention could also be used by subjecting them to a radial force exerted from the outside to the inside thereof, so as to subject them to a radial contraction.

Claims (11)

Clamping ring (1) and holding ring intended to take place in a cylindrical housing (3) made in the base (5a) of a part (5) that one wishes to immobilize relative to a body, this ring (1 ) being formed from a series of successive adjacent cylindrical and / or pseudo-cylindrical elements (7, 9) which are linked together and whose base surface is omega-shaped and thus has an apex (7a, 9a) and two branches (7b, 7c), the tops of these elements (7, 9) being alternately arranged on the outside and on the inside of the ring and respectively forming an external element (7) and an internal element (9) , characterized in that the branches (7b, 7c) connecting two adjacent elements are common and the external elements (7) and the internal elements (9) form "shells" the thickness of which is between 10% and 25% of the width (a) of the vertices (7a) of the external elements (7). Clamping and retaining ring according to Claim 1, characterized in that at least the external elements (7) or the internal elements (9) are cylindrical in shape. Clamping and retaining ring according to Claim 1, characterized in that the external elements (7) or the internal elements (9) are of pseudo-cylindrical shape. Clamping and retaining ring according to any one of the preceding claims, characterized in that the branches (7b, 7c) which connect two adjacent elements (7, 9) are “S” shaped. Clamping and retaining ring according to any one of Claims 1 to 3, characterized in that the branches (7b, 7c) which connect two adjacent elements (7, 9) are rectilinear. Clamping and retaining ring according to any one of the preceding claims, characterized in that the internal face of the walls of the internal or external elements having an apex (7a, 9a) as a base comprises an extra thickness (11). Clamping sleeve implementing a clamping ring (1) according to any one of the preceding claims, characterized in that the ring (1) extends axially on one side of the latter by a leg (55) ending in feet (57). Clamping sleeve according to Claim 7, characterized in that the feet (57) are oriented radially outwards or inwards. Clamping device intended to hold a part (5) and to apply it to a supporting plane (59), the base (5a) of the part (5) being hollowed out of a cylindrical housing (3 ) Receiving a clamping ring according to one of claims 1 to 6 characterized in that it comprises a cylindrical mandrel body (17) hollowed out with an axial bore (31) in which is slidably mounted a piston (27) of which the frustoconical head (29) bears against a frustoconical internal surface of the clamping ring (1), control means being able to move this piston (27) axially so as to exert on the internal surface of the clamping ring (1) a radial force capable of deforming it radially and applying its outer surface against the cylindrical wall of the housing (3) and the base of the part (5) against the supporting plane (59). Clamping device intended to hold a part (5) whose base (5a) is hollowed out of a cylindrical housing (3) receiving the clamping ring (1) of a clamping sleeve (la) according to one of claims 7 or 8, characterized in that it comprises a cylindrical mandrel body (17), one of the ends of which is provided with a boss (19) around which take place the legs (55) of the clamping sleeve (1a), which end with the feet (57) which are pressed against the mandrel body (17), the base (5a) of the part (5) to be maintained resting on one face of a collar (59), the other face of which is itself resting on the mandrel body (17), the latter being hollowed out with an axial bore (25) ) in which is slidably mounted a piston (27) whose frustoconical head (29) bears against the frustoconical internal surface of the ring (1), control means being able to move this piston axially so as to exert on the internal surface of the ring (1) a radial force capable of deforming it radially and applying its external surface against the cylindrical wall of the housing (3). Clamping device according to Claim 10, characterized in that the feet (57) are kept pressed against the mandrel body (17) by the collar (59).

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